# US 9,437,775 B2 · Nitride semiconductor light-emitting device

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- Number: US 9,437,775 B2
- Document ID: US9437775B2
- Status: Granted
- Kind: B2
- Application number: 14/899,364
- Filed: 2014-06-16
- Published: 2016-05-26
- Granted: 2016-09-06
- Earliest claimed: 2013-06-18
- Assignees: Meijo University
- Applicants: Meijo University
- Inventors: Tetsuya Takeuchi; Motoaki Iwaya; Isamu Akasaki
- Web page: https://patentgrep.com/patent/US9437775B2

## CPC

- H10H 20/8162: {Current-blocking structures}
- H01S 5/320225: {polar orientation}
- H01S 5/34333: {with a well layer based on Ga(In)N or Ga(In)P, e.g. blue laser}
- H10H 20/81: Bodies
- H10H 20/812: within the light-emitting regions, e.g. having quantum confinement structures
- H10H 20/818: within the light-emitting regions
- H10H 20/825: containing nitrogen, e.g. GaN
- H01S 5/3054: {p-doping}
- H01S 5/3213: {asymmetric clading layers}
- H01S 5/3409: {special GRINSCH structures}
- H10H: INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
- H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL

## Abstract

An object is to improve a positive hole injection efficiency into an active layer in a nitride semiconductor light-emitting device. The nitride semiconductor light-emitting device is formed by stacking nitride semiconductor crystals each of which contains Al and has a polar or semipolar surface either serving as a growth face. The device includes an active layer (103), and first and second composition-graded layers (102, 104). The active layer (103) is interposed between the first and second composition-graded layers (102, 104). Each one of the first and second composition-graded layers is composition-graded so that an Al composition value is rendered smaller as each one of the first and second composition-graded layers (102, 104) comes close to a side where a sum of spontaneous polarization and piezoelectric polarization is negative.

## Claims

### Claim 1

A nitride semiconductor light-emitting device which is formed by stacking nitride semiconductor crystals in a +c-axis direction, each nitride semiconductor crystal containing Al and having a polar or semipolar surface either serving as a growth face, the device comprising an active layer, a first composition-graded layer and a second composition-graded layer, wherein:
the active layer is interposed between the first and second composition-graded layers; and
each one of the first and second composition-graded layers is composition-graded so that an Al composition value thereof is rendered smaller as each one of the first and second composition-graded layers comes close to a side where a sum of spontaneous polarization and piezoelectric polarization is negative;
the first composition-graded layer has a first interface between the active layer and the first composition-graded layer and a second interface away from the first interface, and the first interface has a larger Al composition value than the second interface; and
the second composition-graded layer has a third interface between the active layer and the second composition-graded layer and a fourth interface away from the third interface and the fourth interface has a smaller Al composition value than the third interface.

### Claim 2 (depends on 1)

The device according to claim 1, further comprising a p-type electron blocking layer disposed to be adjacent to the first or second composition-graded layer, the p-type electron blocking layer being further disposed to be adjacent to the side where the Al composition value is reduced, wherein:
a p-type impurity is doped into the p-type electron blocking layer while the p-type electron blocking layer contains Al;
the p-type electron blocking layer is composition-graded so that an Al composition value thereof is rendered larger as the p-type electron blocking layer comes close to a side which is parted away from the active layer; and
the Al composition value of the p-type electron blocking layer has a maximum value which is larger than the Al composition values of the first and second composition-graded layers.

### Claim 3 (depends on 1)

The device according to claim 1, wherein the first and second composition-graded layers have respective Al composition values at interfaces between each composition-graded layer and the active layer, the Al composition values being substantially equal to each other.

### Claim 4 (depends on 1)

The device according to claim 1, wherein the growth face is a c-plane.

### Claim 5 (depends on 1)

The device according to claim 1, wherein the first and second composition-graded layers are AlGaN layers.

### Claim 6 (depends on 2)

The device according to claim 2, wherein the first and second composition-graded layers have respective Al composition values at interfaces between each composition-graded layer and the active layer, the Al composition values being substantially equal to each other.

### Claim 7 (depends on 6)

The device according to claim 6, wherein the growth face is a c-plane.

### Claim 8 (depends on 7)

The device according to claim 7, wherein the first and second composition-graded layers are AlGaN layers.